Method and apparatus for controlling diameter of pressure rolls



April 23, 1968 N. ROSENSTEIN 3,379,857

METHOD AND APPARATUS FOR CONTROLLING DIAMETER OF PRESSURE ROLLS Filed March 10, 1966 2 Sheets-Sheet l e \r| o Q 4) 43- Q J 4 m M Q M: Q d R m m 3? c cl 7 S4 VH4 f) W W, m

NATHAN ROSENSTElN GiJiQJ ATTORNEYS,

Aprll 23, 1968 N. ROSENSTEIN 3,379,857

METHOD AND APPARATUS FOR CONTROLLING DIAMETER OF PRESSURE ROLLS Filed March 10, 1966 2 Sheets-Sheet 2 MEAS. AMPL.- DET.

2 FCT/Q/CAZ SYSTEM OF 40 51/PPLY R 0 2 REGULATO? DUAL PEA-904! Mai/(Ara? A F MIME/V7016 NATHAN ROSE NSTEIN By @Ja FM ATTORNEY).

United States Patent 3,379,857 METHOD AND APPARATUS FOR CONTROLLING DIAMETER 0F PRESSURE ROLLS Nathan Rosenstein, West Hartford, Conn, assignor to Spunize Company of America, llnc., Unionvilie, Conn., a corporation of Connecticut Filed Mar. 10, 1966, Ser. No. 533,154 6 Claims. (Cl. 219-46?) This invention relates to methods and apparatus for controlling, during operation, the diameter of calender rolls, pressure rolls, textile crimping rolls, and other rolls which are subjected to heat during operation. In at least some of the cases, the rolls are employed in pairs with the material to be processed passing through the nip of the rolls.

More particularly, the present invention is concerned with controlling the diameters of such rolls so that line tangency throughout the nip of the pair of rolls can be maintained during operation, even though the surfaces of the rolls be subjected to high temperatures.

In widely varied fields, where rolls of the type here involved are employed, including the production of films or sheets of rubber, plastic, paper, and the like, and also in certain textile processes, such as those involving filamentary material, it is important and often critical that uniformity of roll diameter be maintained, especially line tangency throughout the nips of the rolls.

The failure to maintain uniformity of roll diameter in adjacent rolls, normally evidenced by warping or bowing of the rolls, creates a condition of non-tangency at the nip, a condition which often produces unwanted deleterious results. This has long been a problem, for example, in calendering rubber or plastic sheeting at relatively high temperatures where small differences in roll diameter across the face of the roll produces undesirable variations in the thickness of the rubber or plastic being calendered.

In the past, attempts have been made to overcome the problem of non-linearity in rolls of the type here involved. Thus, rolls having preset crowned or concave configurations have been used. However, these have not proven entirely satisfactory, primarily because the particular shape selected, while correct for rolling one composition, is not correct for rolling the same composition to a different thickness, or for rolling a different composition to the same thickness.

I have discovered that the diameter of a calender roll is -a function of the differential between the internal temperature of the roll and the surface temperature of the roll. Thus, for example, if during operation in the presence of heat a roll warps and develops a pinch in one portion and a bowing out in another portion, this condition may be due to a difference between the differentials of the surface and internal temperatures at such portions.

I have found that a constant diameter throughout the length of the roll of the type here involved can be obtained by maintaining the surface temperature of the roll at a constant temperature and the interior temperature at a constant temperature. Preferably, both of these temp-eratures should be the same, as nearly equal as possible. However, this is not essential, so long as the difference between the surface and interior temperatures be held constant.

According to my present invention, I provide an improved method and apparatus for maintaining linearity in calender rolls and the like. The improved method includes the steps of continuously sensing the surface temperature of the roll and in response to the temperature sensed of adjusting automatically the heat applied to the surface and also the heat applied to the interior of the roll, thereby to maintain the differential between the surface tem perature and the interior temperature substantially constant, and the differential as small as possible.

It is the object then of this invention to provide a meth- 0d and apparatus for supplying heat to the surface and also to the interior of the calender roll to develop a predetermined wanted surface temperature, for sensing continuously the surface temperature and comparing it with the wanted temperature, and for varying automatically the amount of heat supplied to the surface and to the interior in accordance wih the surface temperature sensed to maintain the temperature at the predetermined wanted value.

Other objects and advantages will appear from the description which follows.

FIG. 1 is a schematic diagram of the electric and fluid pressure control systems;

FIG. 2 is a block diagram of the temperature sensing and electrical control circuit;

FIG. 3 is a schematic diagram showing a mechanism for converting the variable electrical signals into variable pressure signals.

Referring now to the drawings, assume that the machine is fully off, that is, assume the machine is cold and the rolls 1t) and 1 1 are not being driven. As a first step in putting the machine into operation, the rolls l0 and 11 are heated internally. This is done by closing the switch 14- (FIG. 2) to apply power to the heating unit 26 of the fluid reservoir 20 ('FIG. 1), and to turn on pump motor 15 (FIG. 2) which drives the pump 21 (FIG. 1). The fluid in reservoir 20 will be assumed to be oil, but may be water, or steam, or other suitable medium. As this fluid becomes heated and is pumped through the interior of the rolls Ill and 11, the temperature at the surface of the rolls rises. The temperature at the surface of roll 11 is sensed by thermocouple 30, and is observed by the operator at the main recorder 40. When, due to the internal heating, the surface temperature of roll 11 reaches the desired temperature, for example 250 F., the operator starts up the machine by closing the switch 103 (FIG. 1). The rolls 10 and 111 are then driven and electric power is then supplied to heat the rolls It) and Ill externally. N-o electric power is applied to heat the rolls externally unless the rolls are be ing driven.

The rolls it and 11 are shown in FIG. 1 to have their surfaces heated externally by arcuate electric heating shoes 12 and 13 positioned closely adjacent the rolls 10 and 11, respectively. Electric current is supplied to the shoes 12 and 13 from the 240-volt power supply through the switch we and the contacts of relay 105. The contacts of relay 1105 close when the main switch 103 is closed to energize the motor M to drive the rolls. The current supplied to the shoes 12 and 13 is controlled by the rheostat which is adjusted automatically by the pressure controller 91, which is preferably a pneumatic device.

In most cases, the material which is being processed by the rolls it? and 11, such as yarn in a crimper, is unheated aad at ambient temperature, or is cold, and the passage of such unheated material through the heated rolls obviously tends to reduce the surface temperature of the rolls, thereby making it necessary to supply additional heat to maintain the surface temperature constant.

As already mentioned, the rolls 10 and 11 are heated internally by hot fluid, such as hot oil, or hot water, or steam. This fluid is heated electrically at the reservoir 20 by an electrical temperature controller 26 which maintains the fluid at a selected temperature. A thermocouple may, if desired, be used to sense and control the internal temperature. The hot fluid is circulated by pump 21 through the pipe line 22 to and through the interior of the rolls 1t and 11. The running of pump 21 is controlled by relay 25, which in turn is controlled by the main recorder controller 40, as will be described.

Each of the rolls and 11 is hollow, having a fluted inner core forming voids inside an outer shell. The fluid line 22 is connected, as by universal joints, to the hubs of the rolls. The hot fluid enters the roll at the hub, flows through an interior radial passage to the voids in the fluted core, and leaves the roll at the opposite hub, returning to the reservoir by the line 222. The structural details of a hollow roll of the type just described are shown in FIG. 2 of my copending application, Ser. No. 453,128, filed May 4, 1965.

Returning again to FIG. 1 of the present application, a bypass line 23 is provided for controlling the amount of hot oil or other fluid which is circulated through the interior of the rolls 10 and 11. The amount bypassed is controlled by the valve 24, and valve 24 is controlled by the pressure signal developed by the main controller 41 as will be described.

One, or both, of the rolls, the bottom roll as illustrated in FIG. 1, is provided with a thermocouple 31) having a spring-loaded Teflon plunger which is in constant contact with the surface of the roll 11. The thermocouple 30 develops an electrical signal which varies with the surface temperature of the roll 11. The electrical signal is applied by Way of lead 31 to the main controller 411.

Controller 40 is an electro-pneumatic device which receives the electric signal delivered to it from the thermocouple 30 over lead 31, and in response thereto delivers an output pressure signal (air) on output line 41 which varies in a manner corresponding to the variations in the applied electric input signal. The pressure signal in output line 41 is applied to the pressure controller 91 by way of a low-limit pressure relay 80. Relay it is a pneumatic device having an output line 64 which delivers a minimum pressure in response to a regulated pressure applied to the relay over the line 63. This regulated pressure is derived from the source 60, filtered in filter 61, regulated in regulator 62, passed through the solenoid valve 70 to the line 63, and thence to the low limit relay 80.

When, in response to the electric signal delivered over the lead 31 to the controller 40, the pressure in output line 41 is increased to a value higher than that of the regulated pressure in line 63, the low-limit relay 80 delivers on line 64 an output pressure signal which varies in a manner corresponding to the variations in the pressure signal in line 41. The modulated pressure signal thus obtained is applied by Way of line 64 to the pressure cylinder operator 91.

Pressure cylinder operator 91 is a device which compares the pressure signal applied thereto in line 64 against a reference pressure applied as from air supply 160. In response to varying input pressure in line 64, the pressure cylinder operator 91 moves a stern positioner in one direction or the other and to an extent corresponding to the variations in the input air pressure signal. The stem positioner may be a rack 92 which drives a pinion 93 fixed to a shaft 94. Thus, lineal movement of the rack 92 rotates the shaft 94. Fixed to shaft 94 is the rheostat element 95, the position of which controls the magnitude of the current supplied over lead 72 to the roll surface heaters 12 and 13.

When the switch 103 of the textile yarn crimper, or other machine or apparatus of which the rolls 10 and 11 are component parts, is open, and the rolls 10 and 11 are not being driven, the solenoid valve 70 is closed and no pressure is applied to the low-limit pressure relay 89. Hence, no signal pressure is applied to the pressure cylinder operator 91. When the switch 103 is closed to energize the motor M to drive the rolls, the machine-drive contactor relay 101 is energized, the relay contacts 102 close, and current flows through the winding of solenoid valve 70, thereby opening the valve 70 and applying regulated air pressure from regulator 62 to the low-limit pressure relay 80 via line 63 and to the master controller 411 via line 74. The low-limit pressure relay 80 immediately delivers a predetermined low-limit pressure by way of line 64 to the pressure cylinder operator 91, and operator 91 operates to turn the rheostat to its low-limit position. A predetermined low-limit amount of current is thus applied at start-up of the rolls 10, 11, by way of lead 72 to the surface electric heaters 12 and 13 of the rolls 1t) and 11.

The main controller 40, later described in more detail, is a recorder controller which includes an index arm which is pre-set at a selected temperature, the temperature desired for the surface of the rolls 10 and 11. The controller 40 also includes a recording pen 52 (FIGS. 2 and 3) and relay contact control circuits controlled by the electrical signal developed 'by the thermocouple 31) in response to the temperature sensed.

Thermocouple 30 senses the surface temperature of roll 11 and, in response thereto, generates an electrical voltage signal which is applied to the master controller 40 over lead 31. If the voltage developed by the thermocouple 30 is different from a reference voltage preselected and preset in controller 40, the voltage difference is sensed by the controller 49 and in response thereto an adjustment is made in the air pressure delivered by the controller 41} to its output lead 41. For example, if the temreference air pressure is delivered by the low-limit relay sure on line 41 is increased and, as a result, greater than reference air pressure is delivered by the low-limit relay $0 to the line 64 and applied to the pressure cylinder operator 91. The cylinder operator 9'1 then moves the rack 92 in a direction to rotate shaft 94 in the proper direction to adjust rheostat 95 to increase the amount of current applied to the surface heaters 12 and 13.

As the temperature at the surface of roll 11 rises, the change in the electrical signal generated by thermocouple 31 causes arm 51 of the balancing solenoid motor 50 (FIG. 2) to move rotationally, and this moves the disc contacts 16 and 17 (FIG. 2) rotationally. Assume that the desired surface temperature for rolls 1t) and 11 is 250 F. Rotary disc contact 16 is preset at say 4 above the desired temperature, or 254 in the present example. When the surface temperature of roll 11 reaches 254, the rotary disc contact 16 opens the circuit to the relay 25, and the deenergization of relay 25 opens the circuit to the pump motor 15, thereby shutting 01f the pump 21 (FIG. 1). If the surface temperature at roll 11 drops, say 1, the circuit is reestablished, the relay 25 is again energized, and the pump motor 15 is restarted.

As indicated previously in connection with FIG. 1, output pressure signals are developed by controller 40 in lines 41 and 42 in response to the voltage signals from the sensing thermocouple 30. The pressure signal in line 42 is applied through the open solenoid valve 75 to the flow control valve 24 to control the amount of fluid flowing through the bypass line 23. As previously indicated, the first step in start-up of a cold machine, is to turn on the heat to the fluid reservoir 20 and to start the pump 21. No power is supplied to the external electric heaters 12 and 13 unless the rolls 10 and 11 are being driven. And the rolls are not driven until they are first heated internally. When pump 21 is first turned on, valve 24 is closed by air pressure from source 269, and no fluid passes through the bypass line 23.

As the suface temperature of the rolls 10 and 11 increases, this increase is sensed by the thcrmocouple 30, and an increased output pressure from the recorder controller 41) appears in line 42 and is applied to the valve 24 to oppose the pressure from source 260. At a preselected value of pressure in line 42, valve 24 opens to a limited extent to allow a controlled amount of hot fluid to flow through the bypass line 23, thereby reducing the amount of hot fluid which is circulated through the interior of the rolls 11D and 11. This action continues, flow control valve 24 being opened to a greater or lesser extent according to the pressure signal in line 42.

Referring now to FIG. 2, this is a block diagram showing the thermocouple which senses the surface temperature of roll 11 and showing the components of the electrical system which actuates the recorder pen 52, and which drive the rotary disc contacts 16 and 17.

In FIG. 2, all of the components shown, except the thermocouple 3%), are component parts of the main recorder 40 of FIG. 1. Recorder 40 is a commercially available instrument, later specified. Only enough of recorder 40 is illustrated to understand its application to the system being described. The thermocouple 30 converts the temperature sensed into an electrical voltage. This voltage is applied over line 31 to the measuring cir cuit 44 of controller 40 where it is compared directly with the voltage of the standard cell 45. In the measuring circuit 44, two capacitors compare the two voltages. One of the capacitors is a fixed capacitor, the other is a variable capacitor having intermeshed plates insulated from each other. The capacity of the variable capacitor is adjusted by turning one of the stacks, the rotor, to change the extent of intermeshing. The voltage of the standard cell is applied to the variable capacitor. The voltage developed by the thermocouple is applied to the fixed capacitor. After the capacitors are charged, they are discharged into each other through a high speed electronic switch. The amount of charge of each capacitor is a product of the voltage and the electrical capacity. The charge on the fixed capacitor varies directly with the applied voltage. The charge on the variable or balancing capacitor varies only with the value of the capacity since a constant voltage is applied from the standard cell.

Unless the charge on the balancing capacitor is equal to the charge on the fixed capacitor, an unbalance voltage will exist across the capacitors after they have discharged into each other. This unbalance voltage is amplified in the unbalance voltage amplifier 46, is detected in detector 47, amplified in the power amplifier 48, and is applied to the balancing solenoid motor 50. The balancing solenoid motor 54 then adjusts the rotor of the balancing capacitor. This rotor is represented in FIG. 2 by the arm 51, rotatable about its center point. The motor 59 moves the arm 51 in a direction to maintain balance in the circuit, i.e. to maintain the charge on the balancing capacitor equal to the charge on the fixed capacitor. The recording pen 52 is linked directly to the rotary arm 51 of the balancing capacitor and indicates directly the measurement. The capacitors are charged and discharged sixty times a second by a vibrator not shown. Therefore, any unbalance voltage that appears at the detector is of a pulsing nature. The power amplifier circuit 43 is disconnected by a timing contact while the switching is being made and while the capacitors are charging. The electrical system illustrated in FIG. 2 is, as previously indicated, a part of the recorder controller 40 of FIG. 1.

Referring now to FIG. 3, there is shown a very much simplified diagrammatic illustration of the air pressure system of the recorder controller 40. The position of the pen 52, through suitable linkage 34, which is greatly simplified in the diagram, controls the position of the proportioning lever 53. Lever 53 is so mounted as to be movable horizontally and vertically. A suitable mechanism for so mounting lever 53 is shown in US. Patent 2,631,570.

For convenience of discussion, assume that the instrument is balanced and that the pressure in the reset bellows 54 and in the proportioning bellows 55 are equal. When a change occurs in the surface temperature of the roll 11, this change is sensed by the thermocouple 30. The rotor arm 51 of the balancing capacitor (FIG. 2) is moved, and the movement of arm 51 is transmitted to the recording pen 52. As a result, the proportioning lever 53 is moved.

Assume that the surface temperature of roll 11 has increased and that the pen 52 has moved to the left, as viewed in FIGS. 2 and 3. This will move the upper end of the proportioning lever 53 to the right, and cause the upper part of lever 53 to move to the right. This will cause flapper 56 to more nearly cover the nozzle 57, thereby increasing the pressure in line 68 leading to the pressure control relay 58. The diaphragm 67 in relay 58 will move to the right and supply valve 59 will be opened wider. Increased air pressure from input line 74 will pass to the output line 65 until the increased pressure in the proportioning bellows 55 raises the fiexure spring 69 causing it to raise the proportioning lever 53, thereby moving the flapper 56 away from the nozzle 57. The output pressure in line 65 immediately starts to bleed through the adjustable reset resistance 66 into the reset bellows 54. As the pressure in the reset bellows rises, the fiexure spring 69 and the proportioning lever 53 will be moved downward, thereby once more moving the flapper 56 closer to the nozzle 57. This again increases the pressure on the diaphragm 67 of control relay 59 and more air passes to the output 65 until the increased pressure in the proportioning bellows 55 causes it to move the proportioning lever upward once again, thus again moving the flapper 56 away from the nozzle 57. This action continues until the pressure on the diaphragm 67 of the control valve 58 has increased enough to produce the required opening of ball valve 59 which will return the measuring pen 52 to the set point. When this occurs, the pressures in the proportioning and reset bellows 55 and 54 become equal, and equilibrium is again restored. The actions just described occur very fast, practically instantaneously.

It will be seen then that FIG. 2 depicts operative means for sensing the surface temperature of roll 11, for developing a voltage in response to the temperature sensed, and for comparing the volt-age developed with a reference voltage to produce a voltage signal which is related to the reference; that FIG. 3 depicts operative means for converting the voltage signal into pneumatic pressure output signals; and that FIG. 1 depicts operative means for utilizing the pneumatic pressure output signals to control the amount of electrical heat supplied to the surface of the rolls and also to control the quantity of hot oil circulated through the interior of the rolls.

If necessary, a second thermocouple may be placed on the other roll 10. In most cases, only one of the two rolls need be sensed for surface temperature.

If necessary, the rolls, such as 10 and 11, may be surface heated by a plurality of electric heating shoes placed side-by-side. For example, four electric heater shoes, each having a width equal to approximately one-quarter the axial length of the rolls 10 and 11, may be placed on each of the rolls, and four separate thermocouples may be used on roll 11 to sense separately the temperature of each of the four sections. Each thermocouple would then feed a separate electro-pneumatic transducer to produce separate pneumatic signals to control separate rheostats, thereby to control separately the quantity of electrical heating current supplied to each shoe.

Without intending to limit the invention to particular forms of known components, and merely to assure a complete description of one operative embodiment of the system of the present invention, the following information is given:

Thermocouple 30 may be a type RT-CC of the Conax Corporation, Buifalo, N.Y.;

Recorder controller 40 may be a Model 40 Dynalog Recorder of the Foxboro Company, Foxboro, Mass;

The rotary disc contact control circuits in recorder controller 40 (used for controlling the relay 25 which controls the pump 21) may be as described in Technical Information 33-11a, page 1-6, published by the Foxboro Company, and dated September 22, 1964;

Low-limit relay may be a Model 58L of the Moore Products Company, Philadelphia, Pa.

Pressure controller 91 may be a Type EBS lXR Cylinder Operator of the Conoflow Corporation, Philadelphia, Pa;

Rheostat 95 may be a Powerstat, a product of the Superior Electric Company. Alternatively, 95 may be a Variac," a product of General Radio Company, or other rheostat-potentiometer or variable transformer.

The electric temperature controller 26 which controls the temperature of the fluid in reservoir 20 may be a Partlow Model ES or ESR, a product of the Partlow Corporation, of New Hartford, Utica, N.Y.

While the preferred embodiment of this invention has been described in some detail, it will be obvious to one skilled in the art that various modifications may be made without departing from the invention as hereinafter claimed.

I claim:

1. A method of maintaining uniform the diameter of a hollow cylindrical heated roll used in the processing of material having a lower temperature than the surface of the roll, said method comprising the steps of: heating the interior of the roll by circulating hot fluid therethrough; applying electric heat to the external surface of the roll; sensing continuously the temperature of the surface of the roll; developing an electrical signal in response to the temperature sensed; utilizing the developed electric signal to develop a pneumatic pressure signal which varies according to the variations in the electric signal; utilizing the developed pneumatic pressure signal to vary in a corresponding manner the amount of electric heat applied to the roll surface; and also utilizing the developed pneumatic pressure signal to vary the quantity of hot fluid circulated through the interior of the roll.

2. Apparatus for maintaining uniform the diameter of a hollow cylindrical pressure roll, said means comprising: fluid flow means for applying heat to the interior of the roll; electrical heating means for applying heat to the external surface of the roll; sensing means for sensing continuously the temperature of the surface of the roll and for developing an electrical signal which varies in a manner corresponding to the variations in said temperature; an electric current controller for controlling the current to said electrical heating means; a pressure operated controller coupled to said electric current controller; main control means; means for applying said developed electric signal to said main control means for developing a fluid pressure signal which varies in a manner corresponding to variations in the developed electric signal; and means for applying the developed fluid pressure signal to the pressure operated controller for adjusting the electric current controller, to vary the current supplied to the electrical heating means in accordance with the fluid pressure signal developed and applied to the pressure operated controller.

3. Apparatus as claimed in claim 2 characterized in that low limit pressure means are provided for applying at least a predetermined amount of fluid pressure to the pressure operated controller for supplying at least a predetermined quantity of current to the electrical heating means.

4. Apparatus as claimed in claim 3 characterized by the provision of fluid control means for varying the fluid flow to the interior of the roll; and means for utilizing the developed fluid pressure signal to vary the fluid control means.

5. Apparatus as claimed in claim 4 characterized in that said fluid flow means for applying heat to the interior of the roll includes a reservoir of hot liquid, a closed line system interconnecting said reservoir and the interior of the roll, and a pump for circulating said hot liquid through said system.

6. Apparatus as claimed in claim 5 further characterized in that the fluid control means for varying the flow of hot liquid to the interior of the roll includes a bypass line which bypasses the roll; a control valve in the bypass line; and means for applying the fluid pressure signal to the bypass control valve to control the amount of hot liquid diverted through the bypass line.

ANTHONY BARTIS, Primary Examiner.

L. H. BENDER, Assistant Examiner. 

1. A METHOD OF MAINTAINING UNIFORM THE DIAMETER OF A HOLLOW CYLINDRICAL HEATED ROLL USED IN THE PROCESSING OF MATERIAL HAVING A LOWER TEMPERATURE THAN THE SURFACE OF THE ROLL, SAID METHOD COMPRISING THE STEPS OF: HEATING THE INTERIOR OF THE ROLL BY CIRCULATING HOT FLUID THERETHROUGH; APPLYING ELECTRIC HEAT TO THE EXTERNAL SURFACE OF THE ROLL; SENSING CONTINUOUSLY THE TEMPERATURE OF THE SURFACE OF THE ROLL; DEVELOPING AN ELECTRICAL SIGNAL IN RESPONSE TO THE TEMPERATURE SENSED; UTILIZING THE DEVELOPED ELECTRIC SIGNAL TO DEVELOP A PNEUMATIC PRESSURE SIGNAL WHICH VARIES ACCORDING TO THE VARIATIONS IN THE ELECTRICAL SIGNAL; UTILIZING THE DEVELOPED PNEUMATIC PRESSURE SIGNAL TO VARY IN A COR- 